To compare noise levels under real-life conditions we shot this scene with the Canon PowerShot SX150 IS, IXUS 220 HS/ELPH300 HS and IXUS 230 HS/ELPH 310 HS within a few moments of each other
at each of their ISO sensitivity settings.

All three cameras were set to Program auto exposure mode and the lenses were set to approximately the same field of view. The ISO sensitivity was set manually.

The above shot was taken with the the Canon PowerShot SX150 IS in Program auto mode. The lens was set to its widest angle 5mm (28mm equivalent) focal length, the sensitivity set to 80 ISO and the exposure was one second at f3.4. The crops are taken from the area marked with the red square and presented below at 100%.

The first crop shows the PowerShot SX150 IS at its base ISO setting and is slightly underexposed as a result of the 1 second shutter speed limit in Program auto mode. Despite that, you can see good detail in the column on the left, but the wood panelling on the right shows a surprising degree of graininess. On the 100 ISO crop, which received the same exposure the detail is more visible and so is the graininess. The caveat here is that while this may be visible on these 100 percent crops, at smaller magnifications at which photos are more usually viewed and printed, this isn't going to be a problem.

Move up to 200 ISO and the noise goes up a notch. Now you can't help but notice the blotchiness and it's beginning to break into the larger image detail - the grooves between the wood panels are beginning to break up. At 400 ISO it's another step change and this is really the top end for what I'd consider acceptable image quality at any size. The step from 800 to 1600 ISO is another watershed and what you may not be able to see in this final crop in the sequence is the green colour cast that has also crept in.

The story here is that the PowerShot SX150's 14.1 Megapixel CCD sensor starts off with slight visible evidence of noise which then gets progressively worse in quite large steps as you move up the sensitivity scale. If you want relatively noise-free shots from the SX150 IS you'd be advised to stick to the 80 and 100 ISO sensitivites.

Compared with the IXUS 220 HS/ELPH 300 HS and IXUS 230 HS/ELPH 310 HS, both of which share the same 12.1 Megapixel back-illuminated CMOS sensor, the PowerShot SX150 IS' performance looks a little underwhelming. To begin with the PowerShot SX150 100 ISO crop compares very favourably with the crops from the IXUS models and in fact is slightly crisper with better detail. But the CMOS sensors in the IXUS/ELPH models handle increasing ISO sensitivity much better, showing less degradation at each stage with the result that by 400 ISO there's a clear margin in their favour. By 800 ISO the IXUS/ELPH crops are still looking reasonably good where the PowerShot SX150 800 ISO crop is a mass of noisy pixels. The bottom line is that you can shoot with confidence with the IXUS/ELPH models all the way up to 800 ISO and even beyond. Sadly, the same can't be said for the PowerShot SX150 IS.

All three models offer a low light mode. On the PowerShot SX150 Is the resolution is 2 Megapixels and on the IXUS/ELPH models it's 3 Megapixels. As you can see from the crops, as well as higher resolution the IXUS crops show much better detail with significantly less noise. They also offer a Best Image Selection mode which shoots five shots and chooses the best one. For more details of that see our upcoming IXUS 220 HS/ELPH 300 HS and IXUS 230 HS/ELPH 310 HS reviews.